Packaging and sealing are imperative in the efficient functioning of electronic devices, because they provide environmental protection, mechanical stability and thermal insulation to a device. The packaging and sealing material is usually applied on a device while it is a viscous liquid and allowed to cure. The curing process is initiated by simple mixing of polymer resin with a hardener. The resin comprises epoxy moieties and the hardener comprises either amine or acid functionalities. Upon mixing, the facile reaction between the amine functionalities of the hardener and the epoxy functionalities of the resin results in the formation of highly cross-linked polymer network that are known as polymer thermosets (PTs). Such a network is responsible for the desired properties of the PTs, paradoxically they also make the PTs insoluble and infusible. Consequently, thorough removal of PTs without destroying underlying substrate is difficult or impossible, which in turn hinders the reuse of the substrates.
Thus there is a need to remove polymer thermosets completely from substrates without affecting or sacrificing the substrate and its physical and chemical properties. It is also observed that substrates that can be separated from thermosets without damage or loss in properties can result in tremendous economic benefits due to reuse and recycle.
Journal of Applied Polymer Science, Vol. 39, 1425-1437 (1990) and Journal of Applied Polymer Science, Vol. 39, 1439-1457 (1990) describes the reversible cross linking in epoxy resins. They have observed that the S—S bond can be cleaved under harsh conditions.
U.S. Pat. No. 6,841,710, describes a process for degrading polymers of disulphide plastics has been reported, said process comprising adding to the disulphide plastics, an effective amount of a reducing agent having a thiol group and for fracturing the chemical bonds in said plastics and producing a variety of monomers and degradation products wherein said reducing agent is selected from a group of compounds having a thiol group.
US20090137777, discloses a specific poly epoxy compound having at least two olefin oxide groups and at least one tertiary ester group per molecule, a method for producing the compound, a thermosetting resin composition containing the compound, a cured product of the composition, and a method for removing the cured product; wherein said method for removing a cured product, comprises heating the whole or part of the cured product at a temperature higher than the heat-curing temperature to thermally cleave a tertiary ester bond derived from the poly epoxy compound (B), and removing the heated portion of the cured product by using or not using a treatment agent.
Removing polymer thermoset without destroying underlying substrates has not been demonstrated. Also prior art processes execute the process of removal of polymer thermoset at very harsh conditions, which is not very desirable. In fact, the harsh conditions are likely to destroy the substrate, which will eventually make the substrate unavailable for reuse.
Therefore, there is a need to provide agents that will cause cleavage of bonds and thus remove thermosets from substrate without damaging the substrate.
There is also a need to remove polymer thermoset from substrate in such a way that the substrate retains it physical and chemical properties.
Another need is that the agent and the process to remove polymer thermoset from substrate is mild and works in mild process conditions. As mentioned earlier, if the condition is harsh, the substrate is destroyed. Therefore, a mild condition is required for thermoset removal that renders the possibility of substrate reuse.